Treatment of tar



Camif/C u 537905357 5 sheets-'smet 1 Caroiafe TREATMENT OF TAR Filed March 2l, 1934 A. H. RADASCH ET AL April 6, 1937 A. H. RADAscH ET AL 2,075,866

TREATMENT OF TAR Filed March 2l, 1934 5 Sheets-Sheet 2 ATTORNEY April 6, 1937. A. H. RADASCH ET AL TREATMENT OF TAR 1934 5 Sheets-Sheet 5 Filed March 2l (00.556 (wmenser fkfac-Zar fea-andar 5&7/

Wario/ae fram April 6, 1937. A. H. RADAscH ET A; 2,075,866

TREATMENT OF TAR MTQRNE'Y '5 Sheets-Sheet 5 (aas/fc f/rlracar TREATMENT oF TAR /IIL Filed March 2l, 1934 April-6, 1937. A. H. RADAscH ET AL Patented Apr. 6, 1937 UNITED STATES TREATMENT OF TAR Arthur H. Radasch, Bloomfield, and Wilfred M. Bywater, Weehawken, N. J., assignors to The Barrett Company, New York, N. Y., a corporation of New Jersey Application March 21, 1934, Serial No. 716,698 In Canada July 15, 1933 24 Claims.

This invention relates to an improved method of treating liquid hydrocarbon material such as coal tar to recover tar acids from it in the form of carbolates. The tar or other material is heat- 5 ed above its initial boiling point and flashed, vapors are separated from the non-volatilized tar-acid-containing residue and tar acids are distilled from this residue and recovered as carbolate by extraction of the tar acids from the l vapors. By tar acids we mean the volatilizable constituents of tar which form salts with strong alkalies, more particularly, rthe phenols, such as phenol, cresols, and cresylic acids` of commerceor their components. This invention l includes both the method and apparatus for carrying it. out.

More particularly, the invention relates to a process of ashing tar or other hydrocarbon material in which part but not all of the tar acids are vaporized by ashing, tar acids are separated from non-acid constituents in the vapor phase by alkaline extraction of the flashed vapors, and vapors remaining after the alkaline extraction are then used in whole or in part in the inert gas distillation of tar acids from the residueirom the flashing operation.

The process of this invention thus includesl two distilling steps, viz. a primary distillation, which is preferably carried out in a pipe-coil still by heating the tar above its initial boiling point, ashing it and separating the flashed vapors from the undistilled residue, and a secondary distillation in which tar acids are distilled from the residue resulting from the primary distillation. Inert gases which preferably include vapors of non-acid or neutral oil constituents are employed in the secondary distillation.

The process of the present invention is applicable to the treatment of tars such as cokeoven tars, gas-retort tars, vertical-retort tars, and low-temperature tars and other tar-acid and neutral-oil-containing hydrocarbon materials such as coal tar distillates or distillation residues. It may be applied to the treatment of raw moisture-containing tar or stripped tar, etc., or to the separate treatment of tar fractions such as the heavy tar from the collector main of a cokeoven plant or the light tar or tarry oil from the condensers of such a plant. It may be applied to the treatment of mixtures containing coal tar, etc. The invention will be described more particularly as applied to the treatment of cokeoven tar. 55 In the primary distillation or flashing operation of this invention, the tar is heated aboveY its initial boiling point and then ilashed into a vapor-separating chamber. The vapors of lower boiling constituents, which are vaporized by the self-contained heat of the tar at the temperature of iashing, are oollectediseparately froml the undistilled residue. The hot residue is then subjected to inert gas distillation in which` tar acids are volatilized from the residue. The heat for the distillation is preferably supplied by the '10 self-contained heat of the residue, although additional heat may be applied.

The inert gases used in this secondary distillation comprise gases which are inert both to tar acids and to caustic and which serve as a carl5 rier for the tar-acid vapors. Gas 4is used in a broad sense to include fixed gases such as nitrogen and condensable vapors such as steam and oil vapors. The gas introduced into the still includes vapors of neutral oils which repress or 20 minimize the vaporization of neutral oils of the same boiling range from the tar in the still. To the extent that the Vaporizationof neutral oils is repressed, the secondary distillation is selective, and tar acids are distilled from the residue P25 Without the distillation of the corresponding amount of neutral oils. The heat required for the distillation of the tar acids is thus less than that required by the ordinary methods of distillation in which neutral oils of the same boil- 30 ing range as the tar acids are necessarily vaporized in order to distill 01T the tar acids.

An aklaline reagent is brought into contact with the gases and vapors from the inert gas distillation to extract tar-acid vapors and thus "3.5 separate them from the vapors of non-acid constituents. Tar acids are thus extracted in the vapor phase and the carbolateV formed separates from the vapors.

'I'he temperature and concentration of the -40 caustic employed for the vapor phase extraction of the tar acids may be so regulated as-to effect removal of the tar-acid vapors Without substantial condensation of neutral oils in the caustic extractor as a separate oil layer; ordinarily, however, some neutral oil will dissolve in and be removed with the carbolate. If the gases and vapors resulting from the inert gas distillation are cooled, oils will be condensed which may be separately collected. If the gases and vapors from the still are cooled before they enter the caustic extractor, tar-acid oils Will be condensed from them. If they are cooled after tar-acid' vapors have been separated in the caustic tower, y v

neutral oils or oils of low tar-acid content will be obtained.

The vapors from the flashing operation may be similarly treated wit-h an alkaline reagent for 5 the recovery as carbolate of the contained tar acids. The vapors (chiefly of non-acid constituents) remaining after this extraction may advantageously be employed as part of the inert gases used in the distillation of the residue from the iiashing operation.

If the vapors from the flashing operation leave the vapor-separating chamber at a temperature above 200 C. it may be advisable to cool them to this temperature or below before bringing them into contact with the caustic solution in order to prevent the vaporization of too much water from the caustic and the production of a solution so concentrated as to be diicult to handle. In-

stead of cooling the vapors before they enter the caustic tower, the concentration and temperature of the caustic may be so regulated as to effect condensation of neutral` oils in the caustic extractor simultaneously with the extraction of the tar-acid vapors.

Both the caustic extractor employed for extracting the gases and vapors from the secondary distillation and the caustic extractor employed for extracting the vapors from the flashing operation may be operated in a similar manner, i. e. with or without simultaneous condensation of neutral oils or each may be operated diiierently. Furthermore, the caustic extractions can be carried out either as batch operations or as continuous operations with gradual additions of fresh caustic and gradual withdrawal of carbolate from the alkaline liquid; both extractions may be operated alike in this respect or differently. The two tar-acid extraction processes may be carried on independently of each other, using separate caustic feeds to each extractor and collecting separate carbolate fractions. As an alternative method, the same caustic may be employed for extracting tar acids from the two gas streams successively, feeding fresh caustic into one extractor in excess and then employing the unsaturated solution in the other extractor. As a further alternative, the carbolate from both extractions may run to a common receiver and blend therein with the caustic used for the extraction. It is desirable to bring a large volume of caustic into contact with the gases and thus effect a relatively complete absorption of the tar acids from the gases. This is conveniently done by repeatedly recirculating a portion of the caustic-carbolate mixture formed. If the same caustic solution is used in both caustic extractors, the evaporation of water from the solution or condensation of vapors from the gases in one of the caustic extractors may be offset by opposite conditions in the other extractor.

Inert gases may be generated during the treatment of tar owing both to decomposition of the tar and to the vaporization of moisture present in the tar. By providing a vent for the excess gases the apparatus of the inert-gas or secondary distillation will be operated at constant, approximately atmospheric pressure. This secondary distillation is advantageously carried out at atmospheric pressure, although pressures above or below atmospheric pressure will be employed, if desirable, by providing suitable valves and means for removal of material. likewise, the ashing operation, although advantageously carried out at atmospheric pressure may be operated at pres- 75 sures higher or lower than atmospheric. Inert gases such as steam, nitrogen (preferably heated) etc., may be introduced either into the primary or into the secondary distilling system i1 desirable, to aid in the distillation.

Ordinarily the residue from the primary distillation will be at a suiciently high temperature to permit the desired distillation of tar acids by the gases in the secondary distillation without further addition of heat; however, additional heat may be supplied either to the residue or to the gases, if necessary or desirable. According to the preferred method of operation, all of the heat required for the operation is supplied to the tar in a tar heater before the tar is flashed. The heater may be an ordinary direct-fired heater or any other suitable type of heater may be employed such as a heat interchanger in which steam or hot oil, etc. is employed for heating the tar. The waste flue gases from a coke-oven battery or gas-retort plant, etc. or from a tar still may be used for the heating.

By regulating the temperature and rate of supply of the gases, etc., the vaporization of the tar acids from the residue from the flashing operation may be carried to the point where the residue is practically completely stripped or nearly stripped of tar acids, or to the point where chieiiy the lower boiling acids, forA example, phenol and cresols, are removed and recovered. A partial removal of the more readily vaporizable tar acids can be effected with the removal of but a small' quantity of the higher boiling and more difficultly removable acids. By controlling the flashing operation so that the greater portion of the lower boiling tar acids are vaporized and then selectively distilling the lower boiling tar acids from the residue, a high percentage of the lower boiling tar acids can be recovered as carbolate relatively free from higher boiling acids.

According to a preferred method of carrying v out the process, the inert gases employed in the secondary distillation comprise at least a portion of the vapors remaining after the extraction of the vapors produced during the primary distillation. These extracted vapors may be blended with extracted gases and vapors from the secondary distillation and the mixture employed for the secondary distillation. According to the preferred method of operation, the inert gases employed in the process are produced within the process and the addition of steam or nitrogen or other inert gases from some other source is unnecessary.

According to one preferred method of operation, the extracted vapors from the flashing operation are all introduced into the still used for the secondary distillation without the addition of other inert gases. The gases and vapors resulting from the secondary distillation after tar-acid extraction are subjected to total condensation to condense oils and the remaining non-condensable gases are bled to the atmosphere or otherwise treated. As an alternative method of operation, part of the extracted vapors resulting from the secondary distillation are blended With all or a part of the extracted vapors flashed from the tar and used in the inert gas distillation and the balance of the gases and vapors from the secondary distillation are passed through a total condenser and then vented to the atmosphere or otherwise treated. Part or all of the extracted vapors from the ashing operation may be blended with part or all of the gases from the secondary distillation before these gases and vapors pass through the caustic extractor, if desirable. In

:accresce any caseythe extracted vapors ifrom thefiiash- .ing operationmay be subjected to'cooling to condense neutral oils before being .used inthe inert gas distillation. The uncondensed vapors lmay be blendedwith the gases and vapors from the secondarydistillation before or after vthe latter have passed through the caustic extractor. lf blended with these gases and vapors before ,passing 'throughthe caustic extractor; they maybe blend- .are vented to the atmosphere-.or otherwise disposed o-f. Thevented gases .are advantageously cooled to recover their oil 4content before discharging the non-condensable gas to the atmosphere.

Although the primary distillation of this invention is preferably a pipe coil distillation with ashing of the heated tar in a vapor-separating chamber, other methods of distillation may be employed that result in a continuous production of vapors and preferably'a continuous'production of residue also,falthough the withdrawal of-residue from the still may be intermittent.

The invention will be further described in connection with the accompanying drawings which show in a more or less diagrammatic manner apparatus suitable for carrying out the process of the invention but it-is intended and is to .be understood that the vinvention .is not limited thereto.

Fig. l shows a pipe coil still connected with two caustic extractors and means for subjecting the residue from the vapor box of the still to the inert gas distillation of this invention;

`Fig. 2 shows a modified arrangement of tar acid extraction apparatus;

Fig. 3 is a modiiication of the apparatus shown in Fig. 1 equipped with means forvthe condensation of separate neutral oil fractions;

Fig. 4 shows a pipe coil still as in Fig. 1 and two caustic extractors but with a diiferentarrangement of the pipe coil still and the still for treating the residue; and

Fig. 5 shows a modication in which acid oils are condensed.

In Fig. 1 an ordinarytar heater is shown at I. The vapor box 2 is of the type usually employed in connection with a pipe coil still. The residue from the primary distillation is drawn off from the vapor box 2 into the secondary still 3 where it is subjected to distillation by contact with an inert gas. Caustic extractors are shown at 4 and 5. Tar acids flashed from the tar inthe vaporseparating chamber? are extracted in the vapor phase in the caustic extractor 4, and tar acids distilled from the residue in the still l3 during the inert .gas distillation are extracted in the vapor phase in extractor 5.

The caustic extractors may advantageously be towers packed with baiiling means, such as steel screening, over which trickles the caustic-carbolate solution introduced through sprays at the top.

Both extractors may be-operatedin the same general manner, `although since the gases and vapors passing rthrough the caustic extractor 5 usually contain ahigher percentage ofsteam than .those passing through the caustic extractor 4,

caustic .thettempexzatureliconnitions :and cedricentr-ationy of caustic,f;etc.rrmay be= different. `Ingeneral, it-is @advisable pto :recycle throughl each vcaustic ex- .tractor a :.portion ofthe carbolate rformedin it -and blend it withya vsmall amount of fresh' caustic inforder :thattherefwill-be a'large .surface of liquid .-exposed Ato ther-action of the vgases and vapors. .For-this purpose a portion cf thecaustic from thecaust-io extractor 14 is withdrawnr through the pipe Sandrecirculated by thepump l through .the heat ir1terc'harrgcrr8.and sprayed into the .caustic-extractorthrough the sprays 9. Fresh is admitted .preferably continuously, `through .thepipe t6. Similar apparatus is proxvided -for recirculating carbolate `through the caustic extractor 5. Carbolate from the caustic extractor 4 is drawn off into the receiver II and .from .the extractor 5 into the receiver I2. If

vfresh caustic is continuously added to the extiactors the carbolate formed is preferably drawn 01T continuously; if the icausticis added Vbatchwise, the carbolate 1 is .preferable removed vbatchwlse.

The tar enters the system through the pipe I3. .It isheated-in the tar heaterl and then flashed in thevapor box 2. Steamand the vapors of lower boiling constituents of the-tar pass. from the vapor vbox through the line I5 into the caustic extractor 4. Here tar acids are-extracted with caustic or other suitable alkaline reagent. The resulting `gasesincludevapors of neutraloils from which a largegpart or all of the tar-acid vapors have been removed; they pass through the line I6 into the bottom of the still 3.

Hot residue from the vapor box passes through the line I'I into the-still 3 and is distributed by the nozzles I8 over baliling means in the still. Gasesfroni thestill whichinclude tar-acid and neutral oil vapors; pass through the line I9 into the bottom of the caustic extractor 5. The gases vwhich leave thecaustic extractor 5 include vapors of neutral oils from which a large part or all ofthe tar-acidvapors have been removed. They pass through the main 20 into the bottom of the secondary still 3. AGases .from the extractor l which include vapors of neutral oil flashed from the tar in the primary distillation enter the still -3 .through the line I6. A blower 2| is provided to cause circulation of the gases and vapors through the cycle of the still .3 and the caustic extractor 5:

,Instead of combining the steam and neutraloil vapors fromthe flashing operation with the recycled gases ahead of the blower, they may be combined with the recycled gases after they have passed through the blower if desired.

In orderto provide for the elimination from the system of excess inert .gases which include steam generated from water present in the tar, a portion of the recirculated gases is vented through a bleed provided at 22, and a condenser 23 is shown for condensing neutral oils and steam from the gases bled vfrom the system. A decanter v2li is provided for collecting the condensate and separating the neutral oils from water. With the bleed located as shown in the drawings, Vall of the gases from the caustic extractor 4 enter the still 3 and only a portion of the gases V`and vapors of yneutral oils from the caustic extractor 5 pass through the still. A portion of the gases and vapors which leave the caustic extractor 5 are bled from the system and are not recycled through the still 3. The residue from the secondarydistillation in the still 3 is drawn off through the line -25 andcollected in the'receiver 26.

VThe heating of the tar in the tarfheater maybe so regulated that the vapors which pass oi from the vapor box include vapors of tar acids of a more or less denite boiling range so that the carbolate collected in the receiver I| will include the tar acids of this boiling range. Or the prmary distillation may be controlled so that the tar acids in the residue from the flashing operation include tar acids of a particular boiling range, which is a higher boiling range than that of tar acids that are ilashed in the vapor box. Or the inert gas distillation in the still 3 may be so controlled, by regulating the rate at which the gases are circulated through the still 3, as to vaporize a greater or less percentage of the higher boiling tar acids from the residue in this still 3 together with most of the lower boiling tar acids present left in this residue after the iiashing operation. In this manner, the composition of the carbolate collected in the receiver I2 may to some extent be controlled.

Coal tar varies not only in the percentage of its tar-acid content but also in the nature of the tar acids which it contains. With diierent tars different temperature conditions should prevail in order to produce particular results. However, in general, if coke-oven tar is heated in a tar heater sufficiently so that upon ilashing the resultant va-v pors will be at a temperature of say 175 C. and then flashed, the tar acids in the carbolate obtained in the receiver II may comprise a higher percentage of phenol than the tar acids in the carbolate in receiver I2. The temperature to which the tar should be heated to obtain this vapor temperature will be around 25 C. higher, i. e. 200 C.

Fig. 2 shows an arrangement of apparatus especially adapted for obtaining two fractions of carbolate, one containing the major portion of phenol and the other containing higher phenols. The arrangement shown in this figure makes possible an improved fractionation to obtain a phenol fraction especially low in the higher phenols.

In this iigure the legend I0| designates a pipe coil tar heater into which tar may be pumped at Tar leaves the heater I0| by means of a pipe |03 and is passed into a vapor separating chamber |04.

The vapor separating chamber |04 is provided with a reux column |05 of any suitable type, such as a balile tower, a packed tower, or a bell and tray tower. The tower is provided with a liquid inlet |06 for introducing reiiux liquid, and a liquid outlet I0'I having a valve |08 for the removal of reux residue from the base of the reux co1- umn. At or near the top of the column is provided a vapor conduit |09 for the passage of vapors from the reux column to a caustic extractor or phenol absorber I0.

The phenol absorber I I 0 may be of any suitable type, such as described in connection with Fig. 1, for example a packed tower. It is adapted for the passage of vapor up therethrough in counter current to and in intimate contact with a stream of sodium hydroxide solution. The tower I|0 r has a caustic inlet III at or near the top thereof and an outlet |I2 for conducting carbolate to a suitable receiver II3. The Withdrawal of carbolate through conduit ||2 may be controlled by a valve I I4. It is is desired to recirculate caustic which has been used for extraction, it may be withdrawn through recirculating line II5 by means of pump ||6 and reintroduced into the caustic inlet The phenol absorber I I0 has a vapor outlet I i1 for the removal of extracted neutral oil vapors and for their passage to vapor line I|8 to be hereinafter described. A suitable bleeder I|9 and condenser |20 may be provided for condensing a portion of the oil vapors drawn oi through outlet line II'I. Oils thus condensed may be collected in a receiver I2| and employed as reflux liquid in the tower |05. A return pipe line |22 and pump |23 are shown for this purpose.

The vapor separating chamber or flash box |04 is provided with a liquid draw-off |24 for removing residue from the iirst step of the distillation. This draw-off is connected to a spray head |25 at the top of a tower |26 which may be of the packed type or other contact type of tower adapted for the passage of a liquid and gas in countercurrent relation therethrough.

The tower |26 has a draw-oir |21 for removing liquid residue and has at the end adjacent the liquid inlet a conduit |28 for the removal of gases and vapors and for conducting them to a second phenol absorber |29 of type similar to or diierent from phenol absorber |I0. This absorber is provided with a caustic inlet |30 and a draw-off I3l for carbolate for conducting it to a receiver |32. Recirculating line |33 and pump |34 are provided for the recirculation of caustic and carbolate where desired. At or near the top of the tower there is provided a vapor outlet conduit IIS for conducting vapors and gases from the caustic tower back to the extracting tower |26, thus providing a closed circuit between the Vapor extraction tower |26 and the phenol absorption tower |29. A blower |35 may be provided for impelling the gases and vapors through this circuit.

This apparatus is capable of varied operation. However, the following description is given as illustrative of the methods which may be employed for obtaining a plurality of phenolate or carbolate fractions from tar-acidcontaining tar' by means of this process.

Crude coke oven tar containing for example around 3% of tar acids is introduced at |02 into the tar heater IBI and is heated to a temperature of around 275 C.

At this temperature the tar leaves the heater and enters the vapor separating chamber or flash box |04 where a portion of the volatile constituents are vaporized and pass up through the reilux column |05. Residue is withdrawn through draw-oil |24. A suitable quantity of reux liquid is introduced at |06 so that the vapors in passing up through the tower are gradually cooled to a temperature of around 175 C. Because of the presence of lower boiling oils as well as steam from the Water content of ordinary tar this temperature is high enough to maintain phenol, which has a boiling point of l82-183 C., in vapor form. The residue from the reuxing may be withdrawn at |01 at a temperature around 235 C. for example.

Oil bled from the line I|'| may be employed as this reux liquid. When such a liquid is employed, it also undergoes a rectication in its passage down through the tower. Reiiux residue may be withdrawn from the rectifying column |05 by means of outlet |01 and collected as a separate tar-acid-containing oil, or by closing valve |08 this residue may be permitted to overflow into the vapor separating chamber |04 and may then he collected together with the residue from the tar distillation and may be withdrawn together therewith to the tower |26 for the removal of contained higher boiling tar acids.

Alternatively reflux may be supplied by use of a cooling coil in the upper 'part of the column |05; a cooling medium is circulated in this coil to elect partial condensation of vapors in the tower, the condensate flowing downward countercurrent to the ascending vapors.

By the above rectification higher boiling phenols are fractionally removed from the gas stream, the gases and vapors entering the tower ||0 are composed primarily of low boiling oils', and the phenols contained are low boiling phenols, for instance the oil (which is here in vapor form) may have a boiling range of 115 to 200 C. and may also contain some water. With the vapors entering the phenol absorber l0 at a temperature around 175 C. such vapors will constitute around 2 to 6% of the total tar and may contain on the average from 1535% of tar acids based on the oil. Eflicient extraction of these tar acids from the vapors may be obtained in the tower I I0 and these tar acids, about 50% of which, for example, may be phenol, may be withdrawn and collected in receiver ||3.

The dephenolized or extracted vapors are then withdrawn at ||1 and passed to the secondary distillation tower |26. Prior to their introduction into this tower they may be partly cooled to condense a portion of the oils therefrom, if desired, but preferably they are maintained at substantially the temperature they left the phenol absorber, around M55-175 C., and the bleeder |50 and condenser |20 are provided for removing a portion of the oils as condensate and preventing building up of pressure in the system. A portion of this oil condensate may then be returned to the reilux column |05 to serve as reflux liquid.

Residue from vapor separating chamber |04 passes without substantial loss of temperature into the tower |26 where it is brought into intimate contact with the gases and vapors passing up through the tower. This results in the removal from the tar residue of a substantial proportion of the remaining volatile tar-acid constituents.

Where, under the conditions of operation described, reflux liquid is separately withdrawn from tower |05, the residue entering the tower |26 will be a pitch or partly distilled tar amounting to around 85% of the total tar distilled. In this tower |20, for example, about 1% or more of the original tar may be removed as tar acids from the pitch residue by the circulation of the vapors through the tower.

The gases containing these tar-acid vapors, principally tar acids of higher molecular weight than phenol, pass through phenol absorption tower 29 where tar acids are removed and collected as phenolates in receiver |32. The gases and vapors substantially denuded of their taracid content in tower |29 are reintroduced to tower |23 after passing through the line ||8 to the blower |35. By this method of recirculation the removal of neutral oils from the residue introduced into tower |26` is inhibited because of the fact that the vapors brought into contact therewith comprise substantial amounts of vapors of neutral oils. The heat of the residue itself serves to supply the requisite heat of vaporization to the tar acids and thus promotes the separation. Since the gases and vapors entering the extractor tower |26 are substantially free from or lowin tar acids, there is substantially no or at most a relatively low partial pressure of tar acids to inhibit their vaporization and they are thus rapidly vaporized and carried off in the` gas stream.

Fig. 3 is a inodication of the apparatus shown in Fig. 1 and includes separate condensing means for removal of neutral oil from the vapors flashed from the vapor box after the extraction of tar acids and the removal of neutral oil from the of the neutral oil is condensed. The cooling in` the condenser 33 may be regulated to condense any desired fraction of! the neutral oil vapors, but in no case are the vapors cooled below the dewpoint of the gases for steam.

The tar acid extraction in the caustic extractor 4a is preferably so regulated that there is substantially no condensation of neutral oils. `A portion of the carbolate formed in the extractor is recirculated through the heat interchanger 8a and sprayed into the gases and vapors in the caustic extractor through the sprays 9a. Excess carbolate is drawn ofi into the storage tank lla.. Fresh caustic is added at any suitable point in the cycle as through the pipe |0a.

The gases and vapors which pass off from the condenserr 30 contain steam and neutral oils of low boiling range. They pass through the pipe |6a into the still 3a.

The gases and vapors from the still 3a pass rst through the caustic extractor 5a and then through the condenser 3|. In the condenser 3| the cooling of the gases is regulated to condense neutral oils of any desired boiling range. The extraction of tar acids from the gases and vaporsy in the caustic extractor is preferably so regulated that there is no condensation of neutral oils. Caustic is recirculated as described in connection with the caustic extractor 4a of Fig. 3 and excess carbolate is drawn off into the storage tank |2a.

The gases and vapors from the condenser 3| are preferably blended with the gases and vapors from the condenser 30 before reentering the still 3a. Means may be provided for separately in-- troducing the two gas streams into the still3a, if

desirable.

Neutral oils are drawn oir from the condenser 30 into the oil storage tank 32 and neutral oils from the condenser 3| are drawn oft into theV storage tank 33. The condensers 30 and-3| may be of any desirable type. 'Ihey may be heat interchangers in which tar or water is used as the cooling medium. The tar may be preheated by heat interchange with the hot gases and vapors before entering the tar heater |a. Direct contact condensers may be employed in which' case water may be used as the cooling medium or oil which has been condensed from the gases may be cooled and sprayed into the gases and vapors to neutral oil from one of the gas streams, i. e. either from the gases and vapors from the flashing operation or from the inert gas distillation and the other gas stream will then pass'dire'ctly from the caustic extractor to the still 3a.

If desirable, onlyV one condenser may be employed for removing The apparatus of Fig. 4 shows means for blending gases resulting from the vapor phase extraction of tar acids from the, vapors from the flashing operation with the gases and vapors from 5 the inert gas distillation before they are extracted.

The vapors which separate from the residue in the vapor box 2c pass over through the main |5c into the extractor 4c where they are brought into direct and intimate contact with an alkaline reagent capable of extracting the tar acids.

'Ihe neutral-oil vapors remaining after the caustic extraction escape from the extractor 4c through the line |6c. They are eventually, at

l5 least in part, used in the inert gas distillation of the residue from the ilashing operation in the secondary still 3c, but according to the specific example shown in Fig. 4 they are first blended with the gases and vapors coming from this still and'again scrubbed with caustic in the extractor 5c before entering the still.

The residue from the vapor box 2c is subjected to further distillation in the still 3c in an atmosphere of inert gases which includes vapors of neutral oils some of which are vaporized from theV tar in the vapor box 2c and some of which are vaporized in the still 3c and recirculated through the caustic tower 5c. The gases and vapors from this secondary distillation leave the still 3c through the main |9c and are combined with vapors from the caustic extractor 4c and the combined gases pass by the main into the caustic extractor 5c. Carbolate formed is drawn off into the storage tank I2C. Tar acids com- 35 bine with the caustic in the extractor and the remaining gases which include vapors of neutral oils which escape from the caustic extractor are recycled through the still 3c by means of the blower 2|c and the mains 20c and 4|.

4U The blower for circulating the gases and vapors through the dephenolizer and caustic extractor is advantageously located in theline 20c by which the gases and vapors are returned to the still 3c. The blower may, however, be located in the main 40 or elsewhere, as desired.

Neutral oils may be condensed from the system where and as desired, for example in either or both caustic extractors or in coolers provided for this purpose. The recycled inert gases and neutral oil vapors may be reheated as desired before they reenterv the dephenolizer. Modifications of theprocess, such as these, may be made without going beyond the scope of this invention, although the preferred method of operating apparatus such as that shown in Fig. 4 comprises supplying the entire heat for both the primary and secondary distillations to the tar in the tar heater lc and a minimum amount of neutral oils is recovered as such. The residue from the secondary distillation then contains more neutral oils than the residue from an ordinary distillation in which the vaporization of neutral oils is not selectively repressed. The carbolate will ordinarily dissolve some neutral oil, and some neutral oil will be obtained from the vent condenser 23o.

In Fig. 5 provision is made for obtaining taracid oils by cooling vapors from the flashing operation or gases andvapors from the secondary distillation before extraction with caustic or other alkaline reagent. The tar is heated in the heater |11` and flashed in the vapor box 2d. Vapors pass through the main |5d to the condenser 5U where they are subjected to regulated cooling and a tar-acid oil, produced by condensation, is drawn off' into the storage tank 5|. `After this reguagresseL lated cooling the vaporspass through the caustic extractor ddfwhere tar acids are extracted in the vapor phase.. A carbolate formed is collected in the tank Ild. The remaining gases and vapors pass through the main |6d into the secondary still 3d in which the residue from the vapor box 2d is subjected to inert gas distillation.

The gases and vapors from the inert gas distillation in the still 3d pass through the main |911 to the condenser 52 in which tar-acid oils are condensed. These tar-acid oilsk are drawn oi into the storage tank 53. The resulting gases and vapors which still contain vapors or tar'acids are then passed through the caustic extractorV 5d where tar acids are extracted in the vapor phase and recovered as carbolate in the tank 2d. The remaining gases and vapors pass through the main 20d and a portion of .them is combined with vapors from the ilashing operationfand the combined gases are-circulated throughthe secondary still 3d. A bleed condenser 23d is provided for recovering oil from the remainder of the gases and vapors as previously described.

Of the tar acids contained in the vapors entering the condensers, the higher boiling acids are condensed in the acid oils and the lower boiling tar acids are subsequently recovered as carbolate in the extractors. Fig. 5 shows a condenser preceding each of the caustic extractors. Either of these condensers may be omitted. The vapors from the flashing operation may pass through a condenser and caustic extractor and the inert gases from the secondary still may be subjected to extraction without condensation, or the vapors from the secondary still may be subjected to condensation and then extraction while the yvapors from the flashing operation are subjected only to vapor phase extraction without condensation.

Fig. 5 is a somewhat similar to Fig. 1 in that the vapors from both caustic extractors are combined and introduced into the secondary still. Modifications of the apparatus shown in Fig. 4. may include condensers before one or both of the caustic extractors as inFig. 5. By including a condenser between the vapor box 2c and the caustic extractor 4c of Fig. 4, an oil fraction con-- taining the higher boiling tar acids may be col lected from the gases before they enter the caustic extractor 4c. With a condenser in the line |90 to cool the gases from the secondary still before they are combined with the gases in the main |60, a tar-acid'oil may be condensed from these gases and vapors before they are subjected to caustic extraction in the extractor 5c.

Various modications are possible in which the tar or other hydrocarbon material is flashed in the vapor box and the vapors and residue are separated and the residue is treated for its taracid content.

The rate at which gases are circulated through the residue from the first distillation in the inert gas distilling operation will'vary depending upon the temperature ci. the residue treated and the amount of tar acids, etc., recovered. For example, if ordinary coke-oven tar containing three percent of low boiling tar acids is treated and the tar is heated to 175 C. in the tarv heater and then flashed in the vapor box so that the vapors pass off through the main l5 at about 150 C. and the residueis drawn off into the secondary still3 at about C., about 65 percent. of the tar acids can be recovered as carbolate in the receivers and I2 without any substantial amount of neutral oils by circulating the gases through the secondary still at a rate of about 300 cubicfeet per f. Ui

gallon of hot tar to be treated. If the gases are to be cooled for the separate recovery of neutral oil or acid oil and all of the heat for the inert gas distillation is to be supplied by the hot residue, the gases Will be circulated at a greater rate or the tar should be heated to a higher temperature and the gases circulated at the same rate if the same recovery of tar acids is desired. When tar- Yacid oils are condensed, part of the acids are recovered in those oils and part in the form of carbolate. blended with the extracted gases resulting from the inert distillation, then the .temperature and amount of the blended gases must be taken into consideration in calculating the rate at which must also be given consideration. By cooling the gases and vapors from the inert gas distillation to separately recover one or more neutral-oil or acid-oil fractions, a pitch residue of higher or lower melting point may be produced as desired. By cooling the vapors from the rst distillation before introducing them into the secondary still one or more neutral-oil or acid-oil fractions of lower boiling range may be separately recovered.

r"his application is a continuation in part of our copending application, Serial No. 546,448, filed June 24, 1931.

We claim:

1. The method of treating tar-acidand neutral-oil-containing liquid hydrocarbon material which comprises heating the hydrocarbon matei rial above its initial boiling point and flashing the heated material toV vaporize tar acids therefrom, separately collecting the vapors and heated residue, passing vapo-rs thus collected in contact with an alkaline reagent to absorb the tar acid vapors, vaporizing tar acids from the residue in a current of inert gases and bringing the gases containing tar acid vaporsfrom said residue into contact With an alakaline reagent separate from the aforesaid alkaline reagent whereby tar acid vapors are extracted.

2. The method of treating hydrocarbon material, which comprises heating tar-acidand neutral-oil-containing liquid hydrocarbon material above its initial boiling point and flashing the heated material to vaporize tar acids therefrom, separately collecting the vapors and heated residue, passing vapors thus collected in contact with an alkaline reagent to absorb the tar acid vapors, vaporizing tar acids from the residue in a current of inert gases by the heat of the residue and then extracting tar acids from the resulting gases and vapors by an alkaline reagent separate from the aforesaid alkaline reagent.

3. The method of treating hydrocarbon material which comprises heating tar-acidand neutral-oil-containing hydrocarbon material above its initial boiling point and flashing the heated material to vaporize tar acids therefrom, separately collecting the vapors and heated residue, passing vapors thus collected in contact with an alkaline reagent to absorb the tar acid vapors, then vaporizing tar acids from the heated residue in a current of inert gases by the self-contained heat of the residue, extracting tar acids from the resulting gases and vapors by contact with an alkaline reagent separate from the aforesaid alkaline reagent and recycling at least a portion of theremaining vapors of non-acidrconstitutents through the heated residue in admixture with in. ert gases.

If gases from the ashing operation are v 4. The method of Atreating `tar-acidand neutral-oil-containing hydrocarbon material, which comprises distilling the material at a temperature at Which a mixture of vapors of tar acids and neutral oils is evolved therefrom and a hot tar-acid-containing residue remains, separately extracting tar acids from the vapors from this distillation by contact with an alkaline reagent, separately collecting the hot tar-acid-containing residue and bringing at leasta portion of the vapors from which tar acids have been eX- tracted by the aforesaid Contact with alkaline reagent into direct contact with the residue. to aid inthe distillation of tar acids therefrom.-

5. The method of treating tar, which comprises heating coal tar above its initial boiling point and ashing the heated Atar thereby separating vapors of lower boiling. tar acid and neutral oil constituents of the tar from the residue, removing the residue from'the Zone of separation, extracting tar acids from the vapors fromthe fiashing operation by contact with an alkaline reagent While leaving neutral oils in vapor form and using at least a portion of these neutral oil vapors in admixture With inert gases to vaporize tar acids from the residue.

6. The method o-f treating tar, which cornprises heating coal tar above its initial boiling point, flashing the heated tar thereby Vaporizing neutral oils and a portion of the tar acids and producing a hot tar-acid-containing residue, separating the vapors from the residue, removing the residue from the zone of separation, extracting tar acids from the vapors by direct contact With an alkaline reagent, passing at least a portion of the .vapors of neutral oils in admixture With inert gases through the hot residue thereby distilling tar acids from the residue, extracting tar acids from the resulting gases and vapors and recycling through the hot residue a portion of the resulting neutral oil vapors together with vapors of neutral oils from the flashing operation.

'7. The method of treating tar, which comprises heating coal tar above its initial boiling point, ashing the heated tar thereby Vaporizing neutral oils and a portion of the tar acids and producing a hot tar-acid-containing residue, separately collecting the residue and the vapors, passing through the residue a mixture of inert gases 'including 'neutral oil vapors, blending with the resulting gases and vapors, vapors of neutral oils ashed from the tar in 'the flashing operation, extracting tar acids from the blended vapors by contact with an alkaline reagent and recycling through the hot residue from the ashing operation at least a portion of Y the remaining inert gases and vapors of neutral oils to effect the selectivevaporization of tar acids therefrom. Y

8. The method of treating tar, which comprises heating coal tar above its initial boiling point, flashing the heated tar thereby Vaporizing neutral oils and a portion of the tar acids and producing a hot tar-acid-containing residue, separately collecting theresidue from the vapors, selectively vaporizing tar acids from the hot residue by passing therethrough a mixture of inert gases including neutral oil vapors, eX- tracting tar acids vaporized from said residue by contacting the tar acid vapors with an alkaline reagent, blending at least a portion of theremaining neutral oil vapors With vapors of neutral oil flashed from the tar in the flashing y0in-eration and recycling the blended gases through 'the hot residue from the ashing operation to effect the selective vaporization of tar acids therefrom.

9. The method of treating tar, which comprises heating coal tar above its initial boiling point, flashing the heated tar thereby vaporizing neutral oils and a portion of the tar acids and producing a hot tar-acid-containing residue, separately collecting the residue from the vapors, selectively vaporizing tar acids from the 10 hot residue by passing therethrough a mixture of inert gases including neutral oil vapors, extracting tar acids from the resulting gases and vapors by contact with an alkaline reagent, extracting tar acids from the vapors flashed from the heated tar by contact with an alkaline reagent, and passing vapors of neutral oils resulting from both extractions through the heated residue from the flashing operation in eifecting the distillation of tar acids therefrom.

10. The method of treating Wet tar, which comprises heating it to a sufficient temperature to flash off substantially its entire water content, thereby separating steam and vapors of lower boiling constituents of the tar from the non-volatilized residue, separating the vapors from the hot residue, removing the hot residue from the zone of separation and then passing this steam together with vapors of neutral oils through the residue While still hot to distill tar acids therefrom.

11. The method of treating wet coal tar, which comprises heating it in a continuous still to a temperature sufficient to distill olif substantially its entire water content, continuously separating vapors thus produced from the resulting residue, continuously removing residue from the zone of separation, continuously passing at least a portion of the steam thus produced in admixture with neutral oil vapors through the hot residue to distill tar acids therefrom and extracting tar acids from the resulting gases and vapors by contact with an alkaline reagent.

12. The method of treating wet coal tar, which comprises distilling off steam and lower boiling constituents and separating them from the resulting hot residue, removing hot residue from the zone of separation, distilling tar acids from the hot residue in a current oi' this steam mixed with neutral oil vapors, extracting tar acids from the resulting vapors by contact with an alkaline reagent and blending at least a portion of the resulting neutral oil vapors with the steam for the distillation of tar acids from the residue.

13. The method of treating tar, which comprises heating coal tar above its initial boiling point and flashing the heated tar thereby vaporizing vapors of lower boiling tar acid and neutral oil constituents, separating the vapors from the resulting non-volatilized residue, removing residue from the zone of separation, extracting tar acids from these vapors by contact With an alkaline reagent and employing all of the remaining gases resulting from the flashing in the vaporization of tar acids from the residue.

(55 14. The method of treating tar, which comprises heating coal tar above its initial boiling point and flashing the heated tar thereby vaporizing vapors of lower boiling tar acid and neutral oil constituents, separating the vapors from the 7() resulting hot residue, removing residue from the Zone of separation, extracting tar acids from the vapors by contact with an alkaline reagent and introducing inert gases and neutral oil vapors remaining after this tar-acid extraction directly into intimate contact with the hot residue from the ashing' operation together with other inert gases and vapors of neutral oils to vaporize tar acids bythe self-contained heat of the residue therefrom.

15. The method of treating tar, which comprises heating coal tar above its initial boiling point, flashing the heated tar thereby vaporizing neutral oils and a part of the tar acids, leaving a tar-acid-containing residue, separating the vapors from the residue, removing residue from the zone of separation, extracting tar acids from the vapors by contact With an alkaline reagent and then cooling them to separate neutral oil therefrom and using at least a portion of the remaining neutral-oil vapors in the distillation of tar acids from the hot residue.

16. The method of treating tar, which comprises heating coal tar above its initial boiling point, flashing the heated tar thereby vaporizing neutral oils and a part of the tar acids as vapors leaving a tar-acid-containing residue, separating the vapors from the hot residue, removing residue from the zone of separation, extracting tar acids from the vapors by contact with an alkaline reagent, using at least a portion of the resulting vapors of neutral oils in admixture with inert gases to effect the distillation of tar acids from the hot residue, extracting tar acids from the gases and vapors from this inert gas distillation by contact with an alkaline reagent and cooling them to condense a portion of the resulting neutral oils vapors and blending at least a portion of the resulting neutral oil vapors with neutral oil vapors from the flashing operation, and using them in the distillation of tar acids from the hot residue.

17. The method of treating tar, which comprises heating it above its initial boiling point, flashing the tar, separating vapors from the resulting hot residue, removing the residue from the zone o1 separation, distilling tar acids from the residue in a current of inert gases including neutral-oil vapors, extracting tar acids from the resulting gases and vapors by Contact with an alkaline reagent and subjecting them to regulated cooling to separate part but not all of the neutral oil therefrom and recycling at least a portion of the resulting neutral oil vapors through the hot residue, in admixture with inert gases and neutral-oil vapors from the flashing operation.

18. The method of treating tar, which comprises heating it above its initial boiling point to a temperature of about 200 C. or higher, ashing the thus heated tar to vaporize tar acids therefrom, separating vapors from the resulting hot residue, removing residue from the zone of separation, subjecting the separated vapors to a rectification treatment to condense vapors of tar acids while leaving uncondensed vapors of lower boiling tar acids and neutral oils, extracting tar acids from said uncondensed vapors by Contact with an alkaline reagent, distilling tar acids from the aforesaid residue in a current of inert gases, extracting tar acids from the resulting gases and vapors by an alkaline reagent and using remaining gases and vapors in the inert gas distillation of the residue.

19. The method of treating tar to distill it and obtain an acid oil and a carbolate containing tar acids recovered from the tar, which comprises heating it above its initial boiling point and flashing the heated tar to vaporize a portion of the lower boiling tar acids therefrom, separating vapors from the resulting hot residue, removing residue from the zone of separation, distilling tar acids from the residue in a current f inert gases, cooling the resulting gases and vapors to condense part but not all of the oil vapors and to form an acid oil condensate containing a selective fraction of the higher boiling tar acids in said tar, extracting tar acids from the resulting gases and vapors by an alkaline reagent to obtain a carbolate containing a second selective fraction of the higher boiling tar acids in said tar and using remaining gases and vapors in the inert gas distillation of the residue.

20. The method of treating tar to distill it and obtain an acid oil and a carbolate containing tar acids recovered from the tar, which comprises heating it above its initial boiling point and flashing the heated tar to vaporize a portion of the lower boiling tar acids therefrom, separating vapors from the resulting hot residue, removing residue from the zone of separation, cooling the vapors to condense part but not all of the oil vapors contained therein and to form an acid oil condensate containing a selective fraction of the lower boiling tar acids in said tar, extracting tar acids from the resulting vapors by contactl with an alkaline reagent to obtain a carbolate containing a second selective fraction of the lower boiling tar acids in said tar and using at least a part of the remaining vapors in inert gas distillation of the residue.

21. The method of treating tar containing phenols which comprises heating the tar to a temperature sumcient to distill oif a portion of the neutral oils and phenols, separating the vapors from the residue and bringing them into intimate contact with an alkaline reagent, thereby extracting phenols from the vapors so as to form a phenolic extract, passing said residue While still at a high temperature into direct contact with an inert vapor stream whereby additional phenols are evaporated from the residue, bringing the resultant vapor stream containing phenols into intimate contact with an alkaline reagent so as to extract phenols therefrom, and collecting the resultant phenolic extract apart from that obtained in the first mentioned phenol extraction step.

22. The method of treating tar containing phenols which comprises heating the tar to a temperature sufficient so that upon subsequent flashing a pitch residue and a vapor distillate at a temperature substantially above 175 C. are obtained, subjecting the resultant vapors to rectiiication whereby they are partly cooled to a temperature not below about 17 5 C., passing the rectified vapors into intimate contact with an alkaline reagent so as to remove phenols from the vapors and produce substantially phenol-free vapors, passing the residue from said flashing while yet at a high temperature into direct contact with vapors comprising at least a portion of said phenol-free vapors so as to evaporate phenols from said residue and produce a vapor mixture containing phenols, passing said mixture into intimate contact with an alkaline reagent thereby removing phenols from the vapor and producing a second substantially phenol-free vapor and bringing at least a portion of said second substantially phenol-free vapor into contact with said residue toI evaporate phenols from the residue and collecting the phenol product from said second-mentioned phenol removal step apart from the phenol product from said rstmentioned phenol removal step.

23. The method of treating hydrocarbon material, which comprises (1) heating tar-acidand neutral-oil-containing liquid hydrocarbon material to vaporize a portion thereoi", (2) separately collecting the vapors and unvaporized residue, (3) vaporizing tar acids from the residue and separately bringing the vapors from (1) and (3) aforesaid into contact with alkaline reagent to extract tar acid vapors and form carbolates.

24. The method of treating tar which comprises heating it above its initial boiling point to a temperature of about 200 C. or higher, flashing the thus heated tar to vaporize tar acids therefrom, separating vapors from the resulting hot residue, removing residue from the zone of separation, subjecting the separated vapors to' a rectification treatment by direct contact with a neutral oil condensate to condense vapors of tar acids while leaving uncondensed vapors of lower boiling tar acids and neutral oils, extracting tar acids from said uncondensed vapors by an alkaline reagent, cooling at least a portion of the extracted vapors to condense neutral oils therefrom, employing the neutral oil condensate thus obtained for the aforesaid rectification of vapors from the flashing of heated tar, distilling tar acids from the aforesaid residue in a current of inert gases containing neutral oil vapors, extracting tar acids from the resulting gases and vapors by an alkaline reagent and using remaining gases and vapors in the inert gas distillation of said residue.

ARTHUR H. RADASCH.

WILFRED M. BYWATER. 

